1. Technical Field
The present invention relates to a continuously variable gear transmission adapted for land vehicles such as automobiles, motorcycles, and the like.
2. Background Art
There are known, from German laid-open patent application DE-A-30 11 833 and French Patent No. FR-A-692,079, automatic transmissions for vehicles, comprising a planetary gear train interconnecting an input shaft and an output shaft, this gear train comprising at least one gear which is arranged to distribute power, delivered to the input shaft, between the output shaft of the transmission and a balancing subassembly turning at a speed generally different from that of the output shaft.
The balancing subassembly comprises a flywheel of constant or variable inertia. According to these references, the inertia of the flywheel will impose on the planet gears a reaction force which will balance the resistance of the vehicle against movement. In other words, each planet gear will be subjected about its axis to two torques which balance each other, one originating from the inertia of the flywheel, and the other originating from the resistance of the vehicle against movement.
An inertia type of device, such as a flywheel, can generate a reaction force in the desired direction only in response to an accelerating force, assuming negligible mechanical friction and windage losses. However, it is impractical to increase the speed of rotation of the flywheel in order to maintain vehicle movement, because this speed will become prohibitive. Moreover, the engine speeds needed to produce increasingly higher flywheel speeds will also become excessive.
This difficulty was apparently recognized in FR-A-692 079, which proposes, in addition, a centrifugal friction device which, above a certain speed of rotation of the output shaft, ensures a connection (direct coupling) between the inertial flywheel and the output shaft. This direct coupling device does not permit automatic adaptation of the transmission ratio between the input and the output shaft above a given vehicle speed. Moreover, if it is necessary to effect coupling while the flywheel has acquired a substantial speed of rotation, a friction lining provided to ensure coupling with the flywheel will be subjected to considerable wear and heating. There is also the problem of travel at a vehicle speed slightly below the condition causing direct coupling. It would apparently be difficult in this case to operate without slippage between the friction lining and the flywheel.
German laid-open patent application DE-A-27 42 305 (corresponding to U.S. Pat. No. 4,136,751 of POORE et al.) discloses a planetary gear transmission for a construction machinery vehicle which distributes the power produced by a free turbine type gas turbine between a first power path connected directly to the drive wheels of the vehicle and a second power path connected to a hydraulic pump for driving power-consuming auxiliary equipment.
A power transfer assembly selectively couples the drive shaft of the hydraulic pump to the first power path so that the rotational speed of the pump cannot exceed a preselected value. The power transfer assembly includes a friction clutch and a clutch control system that is responsive to the rotational speed of the hydraulic pump shaft to modulatingly regulate the clutch engagement for transferring power from the second power path to the first power path. This transmission system does not include, however, an inertia device, such as a flywheel, in the second power path.